Companion animals are known to suffer from many of the same health conditions as humans. Therefore, it is not uncommon for prevention and treatment methods for dogs and cats to closely follow those for humans. For example, diabetes is one of the most frequently diagnosed endocrinopathies of cats and treatment of diabetes in cats is similar to treatment of diabetes in humans. Human therapies such as insulin therapy, oral hypoglycemics, and dietary modulation of glucose metabolism and weight loss are commonly used in both domestic felines and canines.
Human diets have traditionally been high in carbohydrates, and diets for companion animals, especially cats, have also been high in carbohydrates. In recent years, however, studies have suggested that high carbohydrate intake may be correlated with abnormal glucose metabolism and disease states associated with abnormal glucose metabolism. In response to these studies, diets have been formulated to decrease carbohydrate intake in the hope that decreasing carbohydrate intake will provide a healthier diet and more effectively manage glucose metabolism or its associated disease states.
For humans, the well-known Atkins' diet promotes the use of higher amounts of protein and fat in the diet in order to offset the decreased intake of carbohydrates, resulting in a significantly reduced percentage of caloric intake from carbohydrates even though the diet does not require decreased overall intake of calories. For companion animals, diets such as those described in U.S. Pat. No. 6,203,825, and those provided commercially as Purina DM Diabetes Management Feline Formula (Nestle Purina Pet Care Company), also limit the percentage of calories derived from carbohydrate sources. This type of diet, as described generally in the examples included in U.S. Pat. No. 6,203,825 as Diets 1 through 3, provides a high percentage of calories in the form of dietary fat (Diet 1 (55%), Diet 2 (48%) and Diet 3 (61%). The high percentage of calories from dietary fat puts the animal at risk for unwanted weight gain. This is an indirect side effect of limiting the amount of calories from carbohydrates.
The effect of high fat diets on glucose and insulin concentrations in companion animals has not been characterized. However, there is evidence from human studies that high fat diets may contribute to insulin resistance and lipotoxicity of beta cells, and studies performed in rats have demonstrated that high fat levels in the diet induce insulin resistance in muscle (Youngren et al., “Impaired insulin-receptor autophosphorylation is an early defect in fat-fed, insulin-resistant rats,” J. Appl. Physiol. Vol. 91, p. 2240 (2001)). Furthermore, long-chain free fatty acids are known to interfere with insulin-mediated glucose metabolism, and increased tissue triglycerides have been correlated with development of insulin resistance (Koyama et al., “Tissue triglycerides, insulin resistance, and insulin production: implications for hyperinsulinemia of obesity,” Am. J. Physiol., Vol. 273, E708 (1997)).
Diet restriction has also been described to have a benefit to humans, as well as other animals, by lowering insulin levels and insulin resistance (Reaven et al., “Effect of age and diet on insulin secretion and insulin action in the rat,” Diabetes, Vol. 32, 175 (1983)) and increasing life span and age-associated changes (Kealy et al., “Effects of diet restriction on life span and age-related changes in dogs,” JAVMA, Vol. 220, 1315 (2002)).
For many individuals, both personally and as pet owners, it may be difficult to restrict caloric intake to the necessary levels, no matter how positive the effects might be. Additionally, excessive fat intake can be associated with excess weight gain. Therefore, the need still exists for a dietary method for treating the development of abnormal glucose metabolism and associated conditions (e.g., insulin resistance) or increasing longevity.